Silver superlens using antisymmetric surface plasmon modes.

Silver lenses having super-resolution are analyzed in terms of antisymmetric modes of surface plasmon which have the ability to amplify evanescent waves in UV region. Antisymmetric surface plasmon modes excited by subwavelength grating enhances the resolution and contrast of silver superlens. By using a 20 nm-thick silver superlens, the half-pitch resolution of approximately lambda(0)/8 can be achieved with good contrast at a free space wavelength of 435 nm. The resolution of silver superlens can also be improved using shorter illumination wavelength. We show that the thinner the lens, the better the imaging ability of the silver superlens due to the excitation of antisymmetric surface plasmon modes of higher propagation wave vectors. The thickness of lens is varied from 20 to 40 nm in a three layer system, SiO(2)-Ag-SiO(2). Obtained results illustrate that practical application for patterning periodic structures with good contrast and penetration depth can be achieved by using antisymmetric surface plasmon modes.